chore: remove top level promise await behavior (#11176)

* chore: deprecate top level promise await behaviour

* breaking: remove top level promises await behavior

* types.... err... some of it

* format

* fix changeset

* add back reduced version of the utility type

* fix test

* fix test

* update

* changeset

---------

Co-authored-by: Ben McCann <[email protected]>
Co-authored-by: Simon Holthausen <[email protected]>
Co-authored-by: Rich Harris <[email protected]>

Author: 4 people

.changeset/calm-brooms-burn.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': major
+---
+
+breaking: remove top-level promise awaiting

packages/kit/src/core/sync/write_types/index.js

@@ -480,7 +480,7 @@ function process_node(node, outdir, is_page, proxies, all_pages_have_load = true
 				const from = proxy.modified
 					? `./proxy${replace_ext_with_js(path.basename(file_path))}`
 					: path_to_original(outdir, file_path);
-				const type = `Kit.AwaitedProperties<Awaited<ReturnType<typeof import('${from}').load>>>`;
+				const type = `Kit.LoadProperties<Awaited<ReturnType<typeof import('${from}').load>>>`;
 				return expand ? `Expand<OptionalUnion<EnsureDefined<${type}>>>` : type;
 			} else {
 				return fallback;

packages/kit/src/exports/public.d.ts

@@ -39,20 +39,11 @@ export interface Adapter {
 	adapt(builder: Builder): MaybePromise<void>;
 }
 
-type AwaitedPropertiesUnion<input extends Record<string, any> | void> = input extends void
+export type LoadProperties<input extends Record<string, any> | void> = input extends void
 	? undefined // needs to be undefined, because void will break intellisense
 	: input extends Record<string, any>
-	  ? {
-				[key in keyof input]: Awaited<input[key]>;
-	    }
-	  : {} extends input // handles the any case
-	    ? input
-	    : unknown;
-
-export type AwaitedProperties<input extends Record<string, any> | void> =
-	AwaitedPropertiesUnion<input> extends Record<string, any>
-		? OptionalUnion<AwaitedPropertiesUnion<input>>
-		: AwaitedPropertiesUnion<input>;
+	  ? input
+	  : unknown;
 
 export type AwaitedActions<T extends Record<string, (...args: any) => any>> = OptionalUnion<
 	{

packages/kit/src/runtime/client/client.js

@@ -22,15 +22,14 @@ import {
 	get_link_info,
 	get_router_options,
 	is_external_url,
-	scroll_state,
-	origin
+	origin,
+	scroll_state
 } from './utils.js';
 
 import { base } from '__sveltekit/paths';
 import * as devalue from 'devalue';
 import { compact } from '../../utils/array.js';
 import { validate_page_exports } from '../../utils/exports.js';
-import { unwrap_promises } from '../../utils/promises.js';
 import { HttpError, Redirect } from '../control.js';
 import { INVALIDATED_PARAM, TRAILING_SLASH_PARAM, validate_depends } from '../shared.js';
 import { INDEX_KEY, PRELOAD_PRIORITIES, SCROLL_KEY, SNAPSHOT_KEY } from './constants.js';
@@ -555,7 +554,6 @@ export function create_client(app, target) {
 			} else {
 				data = (await node.universal.load.call(null, load_input)) ?? null;
 			}
-			data = data ? await unwrap_promises(data, route.id) : null;
 		}
 
 		return {

packages/kit/src/runtime/server/page/load_data.js

@@ -1,6 +1,5 @@
-import { disable_search, make_trackable } from '../../../utils/url.js';
-import { unwrap_promises } from '../../../utils/promises.js';
 import { DEV } from 'esm-env';
+import { disable_search, make_trackable } from '../../../utils/url.js';
 import { validate_depends } from '../../shared.js';
 
 /**
@@ -112,16 +111,15 @@ export async function load_server_data({ event, state, node, parent }) {
 		url
 	});
 
-	const data = result ? await unwrap_promises(result, node.server_id) : null;
 	if (__SVELTEKIT_DEV__) {
-		validate_load_response(data, node.server_id);
+		validate_load_response(result, node.server_id);
 	}
 
 	done = true;
 
 	return {
 		type: 'data',
-		data,
+		data: result ?? null,
 		uses,
 		slash: node.server.trailingSlash
 	};
@@ -168,12 +166,11 @@ export async function load_data({
 		parent
 	});
 
-	const data = result ? await unwrap_promises(result, node.universal_id) : null;
 	if (__SVELTEKIT_DEV__) {
-		validate_load_response(data, node.universal_id);
+		validate_load_response(result, node.universal_id);
 	}
 
-	return data;
+	return result ?? null;
 }
 
 /**

packages/kit/src/utils/promises.js

@@ -3,16 +3,16 @@ export async function load({ fetch, url }) {
 		headers: {
 			'x-foo': 'a'
 		}
-	});
+	}).then((r) => r.json());
 
 	const r2 = await fetch(url.pathname, {
 		headers: {
 			'x-foo': 'b'
 		}
-	});
+	}).then((r) => r.json());
 
 	return {
-		a: r1.json(),
-		b: r2.json()
+		a: r1,
+		b: r2
 	};
 }

packages/kit/test/apps/basics/src/routes/load/fetch-cache-control/headers-diff/+page.js

@@ -1,7 +1,7 @@
 /** @type {import('@sveltejs/kit').Load} */
 export async function load({ fetch }) {
 	return {
-		a: fetch('/embed/a').then((x) => x.text()),
-		b: fetch('/embed/b').then((x) => x.text())
+		a: await fetch('/embed/a').then((x) => x.text()),
+		b: await fetch('/embed/b').then((x) => x.text())
 	};
 }

packages/kit/test/apps/embed/src/routes/embed/+page.js

@@ -8,8 +8,8 @@ export const load = async ({ url, fetch }) => {
 
 	return {
 		nav_title: get_nav_title(url),
-		nav_links,
-		banner
+		nav_links: await nav_links,
+		banner: await banner
 	};
 };